nginxproxymanager timing out 30s after POST request

Checklist

• Have you pulled and found the error with jc21/nginx-proxy-manager:latest docker image?
  • Yes
• Are you sure you're not using someone else's docker image?
  • Yes
• Have you searched for similar issues (both open and closed)?
  • Yes

Describe the bug

Have a dockerised Python app behind npm. The app has a feature for uploading a CSV file, which is then processed against an API endpoint. This takes quite a while and the result can be a bit big. I've set up the following in advanced:

proxy_connect_timeout  6000s;
proxy_read_timeout  6000s;
proxy_send_timeout  6000s;
send_timeout  6000s;
proxy_buffer_size 128k;
proxy_buffers 4 128k;
proxy_busy_buffers_size 128k;

No matter what I do I'm getting an Internal Service Error exactly after 30s leading me to believe that npm is not waiting for the reply from the host.

Nginx access log for proxied host
[08/Oct/2024:06:09:58 +0000] - 500 500 - POST https domain.url "/bulk" [Client ip.ip.ip.ip] [Length 141] [Gzip -] [Sent-to ip.ip.ip.ip] "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/129.0.0.0 Safari/537.36" "https://domain.url/bulk"

The function runs properly when accessing the docker image directly (on the exposed port).

Nginx Proxy Manager Version

v2.11.3 © 2024 jc21.com

To Reproduce
N/A

Expected behavior

NPM to properly wait for the response to serve it back to the requestor

Screenshots

Operating System

NPM docker bridged to host network
Python App is also bridged to the host network

Additional context

The issue names no repository files or tests. Start by comparing the CSV POST through Nginx Proxy Manager with the direct Docker-exposed endpoint, then inspect the proxy access log and the configured timeout directives. Done means identifying which component enforces the 30-second failure and defining a reproducible fix or configuration change.